Study On Morphological Characteristics Of Superimposed Expansion In Plastic Zone Of Surrounding Rock Of Repeated Mining Roadway

With the continuous development of modern large-scale mines,in order to meet the needs of efficient production and alleviate the problem of mining tension,the mining roadway driving method of double roadway is widely used in various mining areas.the surrounding rock of the mining roadway that needs to be retained is seriously damaged by repeated mining,which affects the safety of underground work.Therefore,the study of the superimposed expansion morphological characteristics of the surrounding rock of the repeated mining roadway has a certain theoretical guiding significance to ensure the stability control of the surrounding rock of the roadway affected by repeated mining.Taking the 22205 return air roadway in a coal mine as the research background,this paper uses the methods of theoretical research and numerical simulation on the basis of on-site investigation and observation to obtain the surrounding rock stress field and plastic zone distribution of repeated mining roadway in the form of double roadway layout.as a result,the surrounding rock failure distribution law of repeated mining roadway under double roadway layout is obtained.At the same time,through the numerical simulation experiment,the superposition and expansion mechanism of the plastic zone of roadway surrounding rock is further analyzed and verified by engineering,and then the corresponding roadway surrounding rock stability control method is put forward to ensure the safe and efficient production of the mine.The main research results are as follows:(1)The failure stage distribution law of repeated mining roadway is obtained:primary mining and secondary mining are divided into six stages,in which the expansion of plastic zone is the most obvious in the influence stage of primary mining and secondary mining.At the same time,it is concluded that the superimposed expansion characteristic of the plastic zone of the repeated mining roadway is the re-expansion based on the morphological range of the plastic zone of the primary mining under the influence of the secondary mining.(2)The evolution characteristics of superposition and expansion of roadway surrounding rock plastic zone are obtained,and the determination range of each form of roadway surrounding rock superposition expansion is defined.?The evolution characteristics of superposition and expansion of plastic zone in surrounding rock of roadway are obtained:the superposition and expansion of plastic zone in surrounding rock of roadway can be regarded as the second superposition failure on the basis of one failure form,and the superposition failure roughly follows the expansion law of plastic zone in surrounding rock of roadway,that is,under the same surrounding rock parameters,the expansion range of plastic zone is determined by the size of principal stress,and the expansion direction of plastic zone is determined by the size of principal stress Force deflection angle.?The judgment range of each form of roadway surrounding rock superposition expansion is obtained:the ratio of secondary failure confining pressure ratio and primary failure surrounding rock ratio is taken as the judgment standard,it is concluded that,when0.5<?₂/?₁<0.9,the primary plastic zone superimposed secondary plastic zone equals to the superimposed plastic zone;when 0.9<?₂/?₁<1.3,the primary plastic zone superimposed secondary plastic zone equals to the superimposed plastic zone.when?₂/?₁>1.3,the superposition expansion form is?,and the superposition of primary plastic zone and secondary plastic zone is larger than that of superposition plastic zone.?The influence law of the principal stress angle on the superimposed expansion of the surrounding rock of the roadway is obtained:after rotating the principal stress angle under the destroyed condition,the position of the superimposed expanded plastic zone rotates with the principal stress angle and continues to destroy,and the superimposed expansion range of the plastic zone is still applicable after the superimposed expansion.(3)The morphological characteristic mechanism of superimposed expansion of plastic zone of surrounding rock of repeated mining roadway and the phased superimposed expansion mechanism of repeated mining roadway are obtained,the key stages of stability control of surrounding rock of repeated mining roadway are clarified,and the corresponding control methods are put forward.?Under the influence of repeated mining,the surrounding rock of the roadway has formed two stress fields,and the main stress increases and the position of the main stress changes.Under the combined action of the two,the plastic zone expands according to the superposition expansion law on the basis of the failure.?The mechanism of superimposed expansion of staged surrounding rock plastic zone of repeated mining roadway and the key stage of surrounding rock stability control:secondary mining is based on the failure form of primary mining surrounding rock and expands according to the law of superimposed expansion;among them,the lag stability stage of primary mining is the key control stage of surrounding rock stability of repeated mining roadway.?Based on the superposition and expansion characteristics of stage plastic zone of surrounding rock of repeated mining roadway,a step-by-step support method is proposed to control the stability of roadway surrounding rock,which has achieved good results in on-site construction.